Re: [tlug] How much of radiations measured in Central Tokyo?

[Nicolas Limare <nicolas+tlug@example.com>]

> In the sense that *any* radiation escaped, there was a failure of containment.
> That's *very* serious business, and that's why the government has set such
> stringent limits on the amount of radiation that can be detected before making
> a formal report to the regulatory agencies.  But those levels indicate
> "something abnormal," *not* a health risk or an immediate
> catastrophe in the making.

My father, who has been working in the nuclear industry for 30 years
in France and who hapopens to be in Japan now for reasons completely
unrelated to the recent events, tells me that direct radiations are
not a concern if you don't stay close to Fukushima.

Health risks would come from radioactive particles released by the
plant. Human body (and animals and plants) absorb the particles, and
depending on the metabolism will retain them for take days or
months. During this time, these particules irradiate the body from
inside and may (if in high concentration) cause heath problems. That's
why it is advised in directly exposed areas to stay inside, stop
aircon, protect yourself from the rain (the rain washes out particles,
think about the Hiroshima "black rain"). That's also why safety
measures include iodine tabs whose role is to saturate the body in
"clean" iodine and avoid absorbsion of "dirty" iodine by the thyroid.

But these particles are released now in a very low quantity. This is
*absolutely* not like the Chernobyl accident, when the reactor
overheated, the core exploded and pushed the reactor cover, then the
core burned and released particles directly in the atmosphere.

Some of the particles observed now come from the overheating and
melting of the radioactive combustible and steel tubes containing it
*inside* the reactor and leaked out when Fukushima workers decided to
lower the reactor pressure by releasing some gaz. This is a normal
emergency procedure, this release goes through some special filters,
lowering the quantity of hazardous particles.
Some other particles may also have been released when the hydrogen
(also a by-product of the over-headed combustible cracking H₂O in the
reactor) was released when they lowered the pressure, and exploded
*outside* of the reactor, spreading particles (concrete, dust, ...)
from the *external* building. But once again, these are very low
concentrations of radioactive particles.

-- 
Nicolas LIMARE
http://nicolas.limare.net/                         pgp:0xFA423F4F

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